1. Field of the Invention
The invention relates to a filler cap assembly for gas tanks providing a seal which remains undisturbed upon damage to the tank in the area of the filler cap. It also relates to a filler cap assembly having an adapter which can be mounted to a gas tank filler pipe to accept a filler cap, the cap and adapter constructed according to the invention.
2. Description of the Prior Art
Filler cap assemblies used for fuel tanks require that the cap produce a seal when inserted into locked position within a filling opening in the fuel tank. Typically, assemblies of this type include an adapter which is annular in shape and permanently attached to the opening of the fuel tank. The adapter includes a central opening in which the filler cap is seated.
With fuel tanks used in road vehicles such as trucks where there is a possibility of damage to the fuel tank upon the vehicle being involved in an accident, it is necessary that the filler tank construction be such as to avoid leakage of the fuel. One area particularly susceptible to leakage upon damage to the fuel tank is the area around the filler cap. If this area is damaged to the extent of changing the configuration of the sealing surface between the cap and the adapter, leakage of fuel can occur.
A typical prior art filler cap assembly is disclosed in U.S. Pat. No. 3,391,817. Assemblies of this type include a filler cap having an outer surface adapted to telescopically seat within an adapter with the seal between the cap and the adapter being effected along the inner peripheral surface of the adapter. The filler cap as disclosed in the above-referenced patent is one which is constructed for attachment to the adapter of the assembly by a retaining mechanism as opposed to relying on a threaded connection. The retaining mechanism is attached to the lower end of the cap and cooperates with the undersurface of the adapter. When the cap is inserted into the opening of the adapter, a handle on the cap is manipulated to effect locking of the retainer.
A second type of filler cap assembly includes a sealing means on the undersurface of the cap for cooperating with the top of an adapter member. Typical constructions of this type are disclosed in U.S. Pat. Nos. 2,616,583 and 2,616,585. These constructions provide for sealing on an upper surface of the adapter as opposed to an internal surface; but they make no provision for holding the seals upon damage to the tank in the area of assembly. Upon impact, the sealing area will tend to be distorted due to the configuration of the sealing surfaces and their orientation with respect to the remaining structure of the assembly.
A third type of filler cap construction includes an externally threaded surface for mating with a threaded opening in the filler tank. In some circumstances, these constructions are less susceptible to damage causing leakage; but because of the threaded connection, the cap has a tendency to unthread under vibration or wearing of the threaded connection and thus permit leakage.